Which institution has the motto 'Nation Shall Speak Peace Unto Nation'?

The motto 'Nation Shall Speak Peace Unto Nation' is associated with the International Court of Justice (ICJ), which serves as the primary judicial branch of the United Nations. This phrase reflects the court's role in fostering peace and resolving disputes between nations through legal means. The emphasis on dialogue and peaceful resolution encapsulated in this motto highlights the court's mission to promote international cooperation and stability.

The other options pertain to important institutions or landmarks, but they do not share this specific motto. The British Museum focuses on heritage and education, the Parliament of the United Kingdom is concerned with governance and law-making, and Trafalgar Square is a public space known for its historical significance and monuments. None of these entities are designed to mediate disputes between nations, which is distinctly the function of the International Court of Justice.